For more than 2,000 years, a spiky purple plant known as the “liver herb,” has been used in traditional medicine for healing a wide range of conditions from mushroom poisoning to indigestion. Modern researchers have now added the prevention of photo-aging and skin cancer to the long list of milk thistle’s benefits.

Studies from the University of Colorado Cancer Center show that silibinin, a milk thistle extract, protects against skin cancer and photo-aging induced by exposure to UV radiation. It does this by killing skin cells that have mutated due to UVA radiation exposure and by protecting skin cells against damage by UVB radiation.

The researchers explained that when a cell is damaged by UV radiation, it must be repaired or killed so that it cannot go on to cause cancer. Their research shows that the milk thistle extract does both.

One study, published in the journal Photochemistry and Photobiology subjected keratinocytes – human skin cells – to UVA radiation, which makes up about 95 percent of the sun’s radiation that reaches Earth. When the skin cells were pre-treated with silibinin the rate at which the damaged cells died off increased dramatically according to the researchers.

The researchers also noted that silibinin was completely non-toxic to healthy keratinocytes that had not been damaged by the UVA radiation. The silibinin killed only the cells that were mutated and might cause skin cancer or photo-aging. This is another example of nature’s miraculous way of distinguishing between cells that are safe and those that threaten health.

The study showed that silibinin triggered a higher release of reactive oxygen species (ROS) within the damaged cells which led to higher rates of cell death.

Another study by the same authors shows that silibinin reacts differently when it comes to UVB radiation, which makes up about 5 percent of the sun’s radiation that reaches Earth. Instead of killing cells exposed to UVB radiation, milk thistle protects them from DNA damage that can lead to cancer. According to the study published in Molecular Carcinogenesis, it does this by increasing the cells’ expression of the protein interleukin-12, which works to quickly repair damaged cells.

Silibinin is just one of many therapeutic compounds in milk thistle and previous studies show that it may benefit other cancers including, prostate, colon, tongue and breast cancers.

In traditional medicine, milk thistle has been used for toxic and obstructed liver, jaundice, vomiting, pneumonia, flatulence, constipation and hemorrhoids.

Milk thistle is named for the milky sap that oozes from its leaves. It is available at health stores and online in the form of organic seeds, supplements or liquid extract.